Deficit rainfall in the range lesser by 20-59 per cent from mean seasonal rainfall is expected in Ariyalur, Dindigul, Pudukottai, Tirupur and Tutucorin, according to Tamil Nadu Agricultural University.

Tamil Nadu is a rain shadow area of southwest monsoon and nearly 32 per cent of the total annual rainfall of the State is received during this time. Farmers of Dharmapuri, Krishnagiri, Salem, the Nilgris and Kanyakumari are benefited from this seasonal rainfall to take up strategic farm decisions.

The district-level rainfall forecast was developed at Agro Climate Research Centre in the university, based on the Southern Oscillation Index of summer and sea surface temperature values of Pacific and Indian Oceans using Australian Rainman International V.4.3.Software, a university statement said.

The rainfall data collected from the university stations and India Meteorological Department was used to represent the district rainfall information. Rainfall expected during the monsoon is with 60 per cent probability, the statement added.